1. Field of the Invention
The invention relates generally to peripheral devices for use in conjunction with processor controlled systems and more particularly to drivers for reversible polarity loads.
2. Brief Description of the Prior Art
Control of stepping motors and reversible motors in processor implemented systems has heretofore been achieved through unipolar driver interfaces which reversed the polarity of the power supply at each terminal of the motor in response to command signals from a processor.
The use of bipolar drivers for selectively interconnecting a single terminal of a motor with either a positive or negative potential power supply greatly reduced the number of driver components required. A major disadvantage with bipolar drivers was the possibility that, if the system processor generated an illegal, i.e. invalid, control signal, the bipolar driver would link both the positive and negative potentials to the terminal at the same time.
Reliance upon the processor code generation routine alone to inhibit generation of an invalid code was not prudent. Processor and/or programming malfunction raised the potential for creating major damage to the power supplies and the bipolar driver due to the transmittal of an invalid code to the driver.